CN109148952B

CN109148952B - Electrolyte and application and product thereof

Info

Publication number: CN109148952B
Application number: CN201810836287.XA
Authority: CN
Inventors: 沈越; 黄志梅; 黄云辉
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2018-07-26
Filing date: 2018-07-26
Publication date: 2021-02-09
Anticipated expiration: 2038-07-26
Also published as: CN109148952A

Abstract

The invention belongs to the field of secondary batteries, and relates to an electrolyte and application and a product thereof. The additive can form a compact SEI film on the surface of the metal lithium, and can effectively inhibit the decomposition of lithium dendrites, oxygen and electrolyte on the surface of the metal lithium. In addition, the electrolyte is applied to metal lithium batteries and lithium oxygen batteries, the stability of the metal lithium can be obviously improved under the oxygen condition, and the cycle performance is greatly improved.

Description

Electrolyte and application and product thereof

Technical Field

The invention belongs to the field of secondary batteries, and particularly relates to an electrolyte and a metal lithium battery using the same.

Background

Since the first lithium ion battery produced by Sony corporation of japan in 1990, the lithium ion battery has raised a surge of commercialization at home and abroad, and in recent years, the lithium ion battery has been widely applied to various consumer electronics products, partially replaces the conventional fossil fuel, and plays an important role in solving the problems of energy crisis and environmental protection. However, the electrode materials used in commercial lithium ion batteries have limited theoretical specific capacities and energy densities, and cannot meet the increasing demand for high energy densities. Therefore, it is of great interest to develop lithium metal batteries with high energy density as well as lithium oxygen batteries and lithium sulfur batteries.

In the traditional lithium ion battery, the negative electrode adopts commercial graphite with limited theoretical specific capacity (372mAh/g), and compared with the commercial graphite, the metal lithium has higher specific energy and is a metal electrode which has the most potential to replace the graphite negative electrode; but lithium metal causes serious lithium dendrite problems during cycling due to non-uniform deposition of lithium; on the other hand, the lithium metal is easily attacked by oxygen, moisture and electrolyte due to low reduction potential and high reaction activity, so that the practical problems of low coulombic efficiency, short cycle life and the like of the battery are caused. Therefore, improving the stability of metallic lithium in an electrolyte is a problem that must be solved to realize a high specific energy battery.

At present, the protection methods for lithium metal mainly include the following methods: coating a layer of polymer on the surface of the metal lithium to physically block the attack of oxygen and electrolyte; and (3) adding some electrolyte additives to reduce the surface of the lithium metal to generate an SEI film. The former has the defects of complex process, instability in the circulating process and the like, and the SEI film generated by the latter has higher compactness and universality.

The research or development of novel additives is of great significance for the protection of lithium metal of lithium ion batteries.

Disclosure of Invention

The invention provides an electrolyte, application and a product thereof, aiming at providing a novel electrolyte applied to a metal lithium battery, which can effectively and obviously improve the problem of lithium dendrite and protect the metal lithium, thereby comprehensively improving the cycle performance of the metal lithium battery.

To achieve the above object, according to one aspect of the present invention, there is provided an electrolyte comprising an electrolyte additive having at least two hydroxyl functional groups bonded to the same boron atom or at least two hydroxyl functional groups bonded to different boron atoms in a molecular structure.

Further, the electrolyte additive is boric acid, phenylboronic acid or substituted phenylboronic acid, wherein the substituted phenylboronic acid is phenylboronic acid substituted by methoxy and methyl on a benzene ring.

Further, the electrolyte additive comprises boric acid, phenylboronic acid, 4-methoxyphenylboronic acid, 4-methylphenylboronic acid and terephthalocylic acid.

Further, the electrolyte includes an organic solvent and a lithium salt in addition to the electrolyte additive.

Further, the concentration of the electrolyte additive in the electrolyte is 0.001mol L^-1～0.05mol L^-1。

Further, the organic solvent is one or a mixture of more of dimethyl sulfoxide, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, N, N-dimethylacetamide, 1, 3-dioxolane, ethylene carbonate and dimethyl carbonate.

Further, the lithium salt is one or a mixture of more of lithium bistrifluoromethanesulfonylimide, lithium nitrate or lithium hexafluorophosphate.

According to a second aspect of the invention, the electrolyte as described above may be used in a lithium metal battery.

According to a third aspect of the present invention, there is provided a lithium metal battery employing an electrolyte as described above.

The electrolyte of the metal lithium battery comprises an electrolyte additive which is a small molecule, and the small molecule comprises at least two hydroxyl functional groups connected with boron atoms. The electrolyte is particularly applied to a lithium oxygen battery and a lithium sulfur battery system.

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

the electrolyte adopts boric acid or derivatives thereof with cheap raw materials and obvious effect as an additive, and when the electrolyte is applied to a lithium oxygen battery, a layer of compact protective film can be formed on the surface of metal lithium by the substance, and the protective film can inhibit the growth of lithium dendrites and prevent the corrosion and damage of moisture, oxygen and the electrolyte to the metal lithium. At 300mA g^-1The lithium oxygen battery assembled by using the electrolyte can improve the cycle to 146 circles at the current density of (1).

When the electrolyte is applied to a lithium-sulfur battery, a layer of compact protective film is formed on the surface of metal lithium, and the protective film can effectively inhibit lithium dendrites and reduce shuttle reaction of polysulfide, so that the stability of the metal lithium and the cycle performance of the lithium-sulfur battery are improved.

When the electrolyte is applied to a lithium ion battery (lithium iron phosphate), a layer of compact protective film is formed on the surface of metal lithium, and the protective film can effectively inhibit lithium dendrites and improve the stability of the metal lithium and the cycle performance of the lithium iron phosphate battery.

Drawings

FIG. 1 is a schematic diagram of a cell assembly of a symmetric lithium-lithium cell cycled under oxygen conditions;

FIG. 2 is a graph comparing time-voltage curves for a symmetric lithium-ion battery using the electrolyte with a conventional electrolyte;

FIG. 3 is a graph comparing the cycle-voltage-specific capacity curves of a lithium-oxygen battery using the electrolyte with a conventional electrolyte;

FIG. 4 is a digital photograph and scanned picture of a lithium sheet after cycling in a lithium oxygen cell using the electrolyte (a) and a conventional electrolyte (b);

FIG. 5 is a graph showing the effect of different concentrations of additives in the electrolyte on the cycling performance of a lithium-oxygen battery;

fig. 6 is a graph comparing efficiency versus specific capacity curves for lithium iron phosphate batteries using the electrolyte and conventional electrolytes.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Aiming at the problems of lithium dendrite caused by the uneven deposition of lithium in the circulation process of the lithium metal and the problem that the lithium metal is easily attacked by oxygen, moisture and electrolyte, the currently developed additives mainly comprise phosphorus-containing and fluorine-containing compounds, and the compounds are decomposed at a lower potential to form a layer of inorganic substances to cover the surface of the lithium metal.

The invention relates to an electrolyte and a high specific energy metal lithium battery using the electrolyte; the additive in the electrolyte is Boric Acid (BA), phenylboronic acid or one of phenylboronic acids with methoxyl and methyl substituted on benzene rings. The additive can form a compact SEI film on the surface of the metal lithium, and can effectively inhibit the decomposition of lithium dendrites, oxygen and electrolyte on the surface of the metal lithium. In addition, the electrolyte is applied to a metal lithium battery and a lithium oxygen battery, the stability of the metal lithium can be obviously improved under the oxygen condition, and the cycle performance is greatly improved.

Specifically, the compound containing hydroxyl or carboxyl is used as an additive to protect the lithium cathode, the boric acid or the derivative thereof with weak acidity is used as an electrolyte additive, and the O-B-O with an interlaced network structure is formed by adding the compound containing hydroxyl or carboxyl and some oxygen-containing compounds on the surface of lithium into the electrolyte by utilizing the weak acidity of the boric acid and the property of forming the O-B-O3D frame structure with the oxygen-containing compounds, so that the damage of oxygen and moisture in the electrolyte to metal is prevented. The electrolyte can greatly improve the stability of metal in an organic solvent, effectively inhibit lithium dendrite and improve the cycle of a lithium oxygen battery.

The invention provides an electrolyte, which comprises an organic solvent, lithium salt and an additive, wherein the additive comprises one or more of boric acid, phenylboronic acid, 4-methoxyphenylboronic acid, 4-methylphenylboronic acid and phenyl diboronic acid.

Preferably, the organic solvent used when the electrolyte is used in the lithium oxygen battery mainly comprises one of dimethyl sulfoxide, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether and N, N-dimethylacetamide.

Preferably, the organic solvent used when the electrolyte is used in the lithium-sulfur battery is a mixed solvent of diethylene glycol dimethyl ether and 1, 3-dioxolane, and the volume ratio of the diethylene glycol dimethyl ether to the 1, 3-dioxolane is 1: 1.

Preferably, the organic solvent used for lithium metal in the electrolyte solution for lithium deposition and lithium elution experiments is a mixed solvent of ethylene carbonate and diethyl carbonate, and the volume ratio of the ethylene carbonate to the diethyl carbonate is 1: 1.

Preferably, the lithium salt is lithium bistrifluoromethanesulfonylimide.

Preferably, the concentration of the electrolyte additive in the electrolyte is mainly 0.001mol L^-1,0.005mol L^-1，0.01mol L^-1，0.02mol L^-1And 0.05mol L^-1Five kinds of the Chinese herbal medicines are adopted.

The present invention will be described in detail with reference to specific examples. The following examples will help those skilled in the art to further understand the present invention, but the embodiments of the present invention are not limited thereto, and several variations and modifications can be made without departing from the concept of the present invention, which fall within the protection scope of the present invention.

Assembling the lithium-oxygen battery: all operations were performed in a glove box except the cell testing was performed under closed oxygen conditions; using carbon tube sponge with thickness of 0.5mm and area of 3.0x 4.0mm as anode of lithium oxygen battery; and (3) taking the electrolyte soaked by the glass fiber as a diaphragm, taking a lithium sheet with the diameter of 15mm as a negative electrode, stacking the positive electrode shell with the hole, the positive electrode sheet, the diaphragm, the negative electrode, the foamed nickel with the supporting function and the stainless steel negative electrode shell layer by layer, and packaging to obtain the button cell of the lithium oxygen cell.

Assembling a symmetrical lithium-lithium battery: and (3) overlapping the positive electrode shell containing the round hole, the punched lithium sheet, the glass fiber, the non-punched lithium sheet, the foamed nickel and the negative electrode shell layer by layer, and packaging to obtain the lithium-lithium symmetric battery, as shown in figure 1.

Assembling lithium to lithium iron phosphate battery: and rolling and pressing lithium iron phosphate and polytetrafluoroethylene into an electrode plate serving as a positive electrode, soaking a polyethylene diaphragm of an electrolyte, stacking and assembling lithium plates layer by layer in the button cell containing the holes, and packaging to obtain the lithium-iron phosphate lithium battery.

Example 1 (comparative example)

2.87g of lithium bistrifluoromethanesulfonylimide was dissolved in 10mL of dimethyl sulfoxide electrolyte, and the solution was stirred at room temperature for 12 hours to obtain 1.0mol L^-1The electrolyte of (1). The obtained electrolyte is injected into a lithium-lithium symmetric battery to obtain the lithium-lithium symmetric battery of the embodiment.

Testing the lithium-lithium battery under the condition of oxygen saturation, standing for 6 hours, performing charge and discharge test on a LAND-CT2001A tester, and measuring the charge and discharge capacity of 0.25mA cm^-2The current density of (2) was charged and discharged for 2h, respectively.

After the cycle of 40 hours, the polarization of the battery greatly fluctuates, and the battery is short-circuited after 100 hours, and the battery is terminated.

Example 2

The formula of the electrolyte provided by the invention comprises the following components: 0.0123g of boric acid solid is firstly dissolved in 10mL of dimethyl sulfoxide solvent, 2.87g of lithium bistrifluoromethanesulfonimide is then added, and the mixture is stirred for 12 hours at room temperature to obtain 0.02mol L of boric acid^-1Lithium salt concentration of 1.0mol L^-1The electrolyte of (1).

The obtained electrolyte was injected into a lithium-lithium battery to obtain a lithium-lithium battery of this pair of examples.

Testing the lithium-lithium battery under the condition of oxygen saturation, standing for 6 hours, performing charge and discharge test on a LAND-CT2001A tester at the concentration of 0.25mA cm^-2The current density of (2) was charged and discharged for 2h, respectively. After stable cycling for 880h, the polarization of the cell was still below 0.08V.

As shown in fig. 2, fig. 2 is a graph of time-voltage curves of a symmetrical lithium-lithium battery using the electrolyte of example 2 and the conventional electrolyte of example 1, and shows that the addition of boric acid is effective in inhibiting lithium dendrites and blocking corrosion of metal lithium by oxygen and the electrolyte.

Example 3

Prepared in the same manner as in example 2 and contained 0.02mol L^-11.0mol L of boric acid^-1And injecting the electrolyte into a lithium-lithium battery, thereby obtaining the lithium-lithium battery of the present embodiment.

Testing the lithium-lithium battery under the condition of oxygen saturation, standing for 6 hours, performing charge and discharge test on a LAND-CT2001A tester, and measuring the charge and discharge capacity of 0.5mA cm^-2Current density, capacity limit of 0.5mAh cm^-2. The stable circulation is 500 hours, the voltage polarization is stabilized below 0.10V, and the stable circulation is only 48 hours under the same conditions without the electrolyte of the boric acid additive.

Example 4 (comparative example)

1.0mol L of the composition was prepared in the same manner as in example 1^-1A lithium salt electrolyte. The obtained electrolyte was injected into a lithium oxygen battery to obtain a lithium-oxygen battery of this pair of examples.

Testing the sample under oxygen saturation conditionsStanding for 6 hr, testing on LAND-CT2001A tester for charge and discharge at 300mA g^-1Current density, capacity limit 1000mAh g^-1. After 23 cycles, the discharge voltage was below 2V and the cell terminated.

Example 5

Prepared in the same manner as in example 2 and contained 0.005mol L of^-11.0mol L of boric acid^-1A lithium salt electrolyte. The obtained electrolyte was injected into a lithium oxygen battery to obtain a lithium-oxygen battery of this pair of examples.

Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6 hours, and performing charge-discharge test on a LAND-CT2001A tester at a voltage of 300mA g^-1Current density, capacity limit 1000mAh g^-1. The cell can be stably cycled for 146 cycles.

Fig. 3 is a graph comparing the cycle-voltage-specific capacity curves of a lithium-oxygen battery using the electrolyte of example 5 and the conventional electrolyte of example 4. The addition of boric acid is shown to be capable of well protecting the lithium metal negative electrode.

The lithium sheet topography after cycling is shown in fig. 4: the additive can effectively inhibit the corrosion of oxygen, moisture and electrolyte to lithium.

Example 6

Prepared in the same manner as in example 2 to contain 0.01mol of L^-11.0mol L of boric acid^-1A lithium salt electrolyte. The obtained electrolyte was injected into a lithium oxygen battery to obtain a lithium-oxygen battery of this pair of examples.

Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6 hours, and performing charge-discharge test on a LAND-CT2001A tester at a voltage of 300mA g^-1Current density, capacity limit 1000mAh g^-1. The cell can be cycled for 121 cycles stably.

Example 7

Prepared in the same manner as in example 2 and contained 0.02mol L^-11.0mol L of boric acid^-1A lithium salt electrolyte. The obtained electrolyte was injected into a lithium oxygen battery to obtain a lithium-oxygen battery of this pair of examples.

Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6 hours, and performing charge-discharge test on a LAND-CT2001A tester at a voltage of 300mA g^-1Current density, capacity limit 1000mAh g^-1. The cell can be stably cycled for 109 cycles. As shown in the cyclical graph of fig. 5.

Example 8

Prepared in the same manner as in example 2 and contained 0.05mol of L^-11.0mol L of boric acid^-1A lithium salt electrolyte. The obtained electrolyte was injected into a lithium oxygen battery to obtain a lithium-oxygen battery of this pair of examples. Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6 hours, and performing charge-discharge test on a LAND-CT2001A tester at a voltage of 300mA g^-1Current density, capacity limit 1000mAh g^-1. The cell can be cycled for 121 cycles stably. As shown in the cyclical graph of fig. 5.

Fig. 5 shows the effect of different concentrations of additives in the electrolytes of examples 6, 7 and 8 on the cycle performance of the lithium-oxygen battery, and it can be seen from the figure that the cycle performance of the lithium-oxygen battery can be improved when the concentration of boric acid is between 5mM and 50mM, but the cycle performance of the lithium-oxygen battery is improved most when the concentration is controlled to be 20 mM. It is shown that the addition of boric acid does protect the lithium metal negative electrode very well. Inhibit lithium dendrites and mitigate corrosion of metallic lithium by oxygen and electrolyte.

Example 9

Prepared in the same manner as in example 2 and contained 0.02mol L^-11.0mol L of boric acid^-1A lithium salt electrolyte. And injecting the obtained electrolyte into a lithium-iron phosphate lithium battery to obtain the lithium-iron phosphate lithium battery of the embodiment.

The lithium-iron phosphate lithium battery is tested under the condition of oxygen saturation, and after standing for 6 hours, a charge-discharge test is carried out on a LAND-CT2001A tester, and the charge and discharge are carried out at a multiplying power of 0.5C. After the battery is stably cycled for 200 circles, the specific capacity is still 87mAh/g, and 1.0mol L of the conventional electrolyte (example 4) is used^-1Under the same test condition, the capacity of the dimethyl sulfoxide electrolyte of the lithium bistrifluoromethanesulfonimide is only after 200 cyclesHas 56 mAh/g.

Fig. 6 is a comparison graph of efficiency-specific capacity curves of an electrolyte containing boric acid (example 3) and a conventional electrolyte (example 4) used in a lithium iron phosphate battery, and it can be seen from the graph that the stability of metal lithium can be improved by adding boric acid, corrosion of a dimethyl sulfoxide electrolyte to a metal lithium sheet is avoided, and the cycling stability of lithium iron phosphate is improved to a certain extent.

Example 10

Prepared in the same manner as in example 2 and contained 0.02mol L^-11.0mol L of terephthalic acid^-1A lithium salt electrolyte. The obtained electrolyte was injected into a lithium oxygen battery to obtain a lithium-oxygen battery of this pair of examples.

Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6 hours, and performing charge-discharge test on a LAND-CT2001A tester at a voltage of 300mA g^-1Current density, capacity limit 1000mAh g^-1. The cell can be stably cycled for 81 cycles.

But using the usual 1.0mol L^-1The dimethyl sulfoxide electrolyte of the lithium bistrifluoromethanesulfonimide circulates for 23 circles under the same test conditions.

Example 11

0.0123g of boric acid solid is firstly dissolved in 10mL of diethylene glycol dimethyl ether solvent, 2.87g of lithium bistrifluoromethanesulfonimide is then added, and the mixture is stirred for 12 hours at room temperature to obtain 0.02mol L of boric acid solid^-11.0mol L of boric acid^-1An electrolyte of a lithium salt. The obtained electrolytic solution was injected into a battery to obtain a lithium-oxygen battery of the present example.

Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6 hours, and performing charge-discharge test on a LAND-CT2001A tester at a voltage of 300mA g^-1Current density, capacity limit 1000mAh g^-1. The cell can be cycled for 155 cycles stably.

But using the usual 1.0mol L^-1Under the same test conditions, the diethylene glycol dimethyl ether electrolyte of the lithium bistrifluoromethanesulfonimide circulates for only 32 circles.

Example 12

0.0123g of boric acid solid is firstly dissolved in 10mL of solvent of tetraethylene glycol dimethyl ether, 2.87g of lithium bistrifluoromethanesulfonimide is then added, and the mixture is stirred for 12 hours at room temperature to obtain 0.02mol L of boric acid solid^-11.0mol L of boric acid^-1An electrolyte of a lithium salt. The obtained electrolytic solution was injected into a lithium-oxygen battery to obtain a lithium-oxygen battery of the present example.

Testing the lithium-oxygen battery under the condition of oxygen saturation, standing for 6 hours, performing charge and discharge test on a LAND-CT2001A tester, and measuring the voltage at 200mA g^-1Current density, capacity limit 1000mAh g^-1. The cell can be stably cycled for 75 cycles.

But using the usual 1.0mol L^-1The tetraglyme electrolyte of lithium bistrifluoromethanesulfonylimide circulates for only 40 circles under the same test conditions.

Example 13

0.0123g of boric acid solid was dissolved in 10ml of a mixed solvent of diethylene glycol dimethyl ether and 1, 3-dioxolane (volume ratio: 1)), and 2.87g of lithium bistrifluoromethanesulfonimide was added thereto and the mixture was stirred at room temperature for 12 hours to obtain 0.02mol L of a solution^-11.0mol L of boric acid^-1And injecting the obtained electrolyte into the lithium-sulfur battery, wherein the positive electrode is made of a composite positive electrode material made of a vulcanized polyacrylonitrile material, and the negative electrode is made of a lithium sheet, so as to obtain the lithium-sulfur battery of the embodiment.

And performing charge and discharge tests on a LAND-CT2001A tester, wherein the voltage interval is set to be 1-3V, the voltage is cycled for 200 circles under the magnification of 0.2C, and the capacity retention rate is 85%.

Compared with the common electrolyte without boric acid, the electrolyte can be circulated for 200 circles under the same condition, and the capacity retention rate is only 50%.

Example 14

0.0123g of boric acid solid was dissolved in 10ml of a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio: 1)), 2.87g of lithium bistrifluoromethanesulfonylimide was added thereto, and the mixture was stirred at room temperature for 12 hours to obtain a solution having a concentration of 0.02mol L^-11.0mol L of boric acid^-1An electrolyte of lithium salt, and injecting the electrolyte into a lithium-lithium sealed battery system.

0.5mA cm^-2After 600h of cycling, the battery polarization was below 0.04V, while using a conventional carbonate electrolyte, the battery was cycled for only 260h under the same conditions.

In the same way, the replacement of boric acid by phenylboronic acid, 4-methoxyphenylboronic acid, 4-methylphenylboronic acid or phenylboronic acid can relieve the corrosion degree of metal lithium and improve the cycle performance of the battery. Test analysis shows that the electrolyte additive can react with hydroxyl or oxygen-containing compounds on the surface of a lithium sheet to obtain compounds containing B-O-B or O-B-O covalent bonds, and the compounds formed in situ have hydrophobicity and ionic conductivity to a certain extent and can prevent moisture, oxygen and electrolyte from corroding metal lithium.

In conclusion, the electrolyte disclosed by the invention adopts the boric acid with lower price as an additive, is used for protecting the negative electrodes of the metal lithium battery, the lithium-oxygen battery and the lithium-sulfur battery, and can effectively inhibit the corrosion of oxygen, moisture and the electrolyte to the metal lithium. Meanwhile, the electrolyte is applied to a lithium-sulfur battery, and can effectively inhibit the corrosion of polysulfide compounds on metal lithium.

Compared with the prior method for protecting the lithium metal, the method has the advantages of simple process, low price and obvious effect. The lithium-lithium battery assembled by using the electrolyte can be stably circulated for 880h, and the cycle life of the lithium-lithium battery is 8 times that of the common electrolyte; moreover, the lithium-oxygen battery assembled by using the electrolyte has 146 cycles of capacity-limiting circulation, which is more than 6 times that of the common electrolyte.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A metal lithium battery, characterized in that it uses an electrolyte, characterized in that the electrolyte contains an electrolyte additive, the electrolyte additive contains at least two hydroxyl functional groups on the molecular structure, which are bound to the same boron atom or to different boron atoms;

the electrolyte additive is boric acid, phenylboronic acid or substituted phenylboronic acid, wherein the substituted phenylboronic acid is a product of substituting a methoxy group or a methyl group on a benzene ring of the phenylboronic acid;

the concentration of the electrolyte additive in the electrolyte is 0.001mol L^-1～0.05mol L^-1。

2. The lithium metal battery of claim 1, wherein the electrolyte additive comprises boric acid, phenylboronic acid, 4-methoxyphenylboronic acid, 4-methylphenylboronic acid, and terephthaloboric acid.

3. A lithium metal battery according to any of claims 1-2, characterized in that the electrolyte comprises, in addition to electrolyte additives, an organic solvent and a lithium salt.

4. The lithium metal battery of claim 3, wherein the organic solvent is one or more selected from the group consisting of dimethyl sulfoxide, tetraglyme, diethylene glycol dimethyl ether, N, N-dimethylacetamide, 1, 3-dioxolane, ethylene carbonate, and dimethyl carbonate.

5. The lithium metal battery of claim 4, wherein the lithium salt is one or a mixture of lithium bistrifluoromethanesulfonylimide, lithium nitrate or lithium hexafluorophosphate.